Study On The Risk Assessment And Protection Of Dangerous Rockfall Hazards Of Railway In Mountainous Areas

The railway is an important transport facility in China,and its technical advantages of large transport volume and fast transport speed make it the backbone of China’s transport system.Railway construction projects are becoming more and more frequent and extend to mountainous and remote areas,but the construction lines are susceptible to geological hazards,causing huge losses,among which the railway rock hazard is particularly serious.Geological hazard evaluation is a very important task in railway construction.To improve the standardization of railway safety management,speed up railway development,guarantee the high requirements of people’s travel quality,practice the spirit of"safe and high quality,develop the road and strengthen the country",identify the impact factors of railway rock hazard,construct a system of hazard evaluation indexes for railway rock hazard in mountainous areas,and evaluate the risk of the rock hazard.It is of great significance to identify the factors affecting railway rockfall hazards,to build a hazard evaluation index system for railway rockfall hazards in mountainous areas to study the hazard level,to improve the protection ability against railway rockfall hazards,to strengthen railway safety production in all aspects and to guarantee the railway operation safety.This thesis takes railways in mountainous areas as the research background and takes rockfall hazards and their threatening environment as the research object.Based on discussing the current research status of railway rockfall hazards,the study constructs an evaluation index system for railway rockfall hazards in mountainous areas and classifies them into evaluation levels,and explores the protection technology for railway rockfall hazards.The combination of principal component analysis and information substitutability is used to establish the index screening model,and the weighting calculation is based on the combination of"improved G2 method-inverse entropy weight method（EWM）-game theory",and the topo cloud model is used to evaluate and grade the disaster situation in the study section.The evaluation results were verified by using the entropy-weighted TOPSIS model.The main findings of this paper are as follows:（1）Establishing the index system for evaluating the hazard of dangerous rock fall hazards of railways in mountainous areas.The initial index system containing 23 influencing factors was established by analyzing the literature,and the initial index system was filtered by using principal component analysis and information substitutability to eliminate the indexes that have little influence on the evaluation results of hazard levels and those with overlapping descriptive information,and finally,a railway rockfall hazard evaluation index system containing 11 evaluation indexes was constructed.Concerning the current national industry norms,relevant literature studies,and expert opinions,the hazard level of railway rockfall hazards is divided into 4 levels:Ⅰ（safe）,Ⅱ（less safe）,Ⅲ（dangerous）,andⅣ（extremely dangerous）.（2）To summarize the design of protection works for railway rockfall hazards in mountainous areas.To clarify the overall protection idea of the dangerous rock fall hazards in the study area,and to uphold the principle of prevention as the main objective when designing protection engineering for dangerous rock fall hazards in the study area,combining protection and avoidance,reflecting the specificity of single dangerous rock body protection,while maintaining the macro correlation of group dangerous rock body protection,and taking corresponding protection measures according to the severity and danger level of dangerous rock bodies.（3）Constructing a model for evaluating the hazard of dangerous rock fall hazards based on the topologic cloud theory.The combination of"improved G2-inverse entropy weight-game theory"is used to assign weights to each index,and the posable cloud evaluation model is used to solve the randomness and fuzziness of the uncertainty problem,and also to achieve a unified quantitative description between evaluation indexes and evaluation levels.TOPSIS comparative analysis model is established to verify and analyze the evaluation results.（4）Based on the section of Qiangui Railway from K186+232.5（Damo）to K245+240.3（Siting）,an example analysis was carried out.Six typical hazard sites were selected for the evaluation of rock fall hazards,and the evaluation results were:P₁ and P₃ rock fall hazards were ratedⅠ（safe）,P₂,P₄,and P₅ rock fall hazards were ratedⅡ（less safe）and P₆ rock fall hazards were ratedⅢ（more dangerous）,and the corresponding protection engineering design was carried out for each hazard site according to the evaluation results.